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Wednesday, January 23, 2013

Let's continue the theme of two recent postings, the clash between what we know about physics, and UFO claims and beliefs.

In Is there a Warp Drive In your Future? (December 2), UCSD physics professor Tom Murphy examines the claim, "If it can be imagined, it can be done." He reports, "It took me all of two seconds to violate this dictum as I imagined myself jumping straight up to the Moon... I wondered how pervasive this attitude was among physics students and faculty. So I put together a survey. The overriding theme: experts say don't count on a Star Trek future."

Then in Is Interstellar Travel 'Preposterous'? (December 29), we examine three "classic" papers written by physicists in the 1960s, discussing the feasibility of interstellar travel. Nobel laureate Edward M. Purcell examines the difficulties posed not by technological limitations, but by fundamental laws of physics, and pronounces the idea "preposterous."

Echoing the points made fifty years ago by Purcell, Von Hoerner, and Markowitz, Gainer reminds us

The basic principles of physics are applicable independently of where in the galaxy a stellar system is located and will not change over time. Newton’s three laws of motion and the conservation of energy are descriptions of the manner in which different parts of a physical system interact. Consequently, a model based on an exploratory expedition leaving Earth would apply equally to all planetary systems in our galaxy. Any culture, no matter how advanced in technology, would face the same constraints imposed by physics.

He starts with the assumption that a vessel to make such a trip would need to have a mass at least about 100 times that of America's late Space Shuttle, with its living quarters, life support, nuclear fusion reactor, etc. Assume we want to travel to a star system 10 light years away at 0.5c, a trip that would take about 20 years, "For propulsion of the hypothetical spacecraft the blast energy would have to be converted, with near 100% efficiency, to a constrained unidirectional particle beam with thrust pulses of 1.8 megatons per second for 174 days." But here is the rub (and here is what upsets the Star Trek Skeptics crowd): "There is no possible material construction that can constrain and direct the thermal and blast energy of the nuclear fusion rate required for interstellar travel. Consequently, I conclude that alien spacecraft cannot exist." This agrees exactly with what the physics Nobel Laureate Edward M. Purcell explained to us fifty years ago.

But some people who self-identify as skeptics don't want to hear anything like this. Immediately following Gainer's E-Skeptic article is a "rebuttal" to Gainer by Peter Huston, whose degree is not in the physical sciences, but in Asian Studies. Huston objects,

To a non-physicist such as myself, the obvious questions are “Why is such a material impossible?” and “Why is thermonuclear power the only feasible power source?”

To answer these questions, he turned to science fiction writer Carl Fredrick, who is also a retired physics professor. Summarizing Fredrick's response, Huston writes:

First, to assume that something is impossible because current technology, as opposed to the known laws of physics, doesn’t allow it is “silly.” Other points were that there is a great deal of research being done into controlled fusion and that might considerably change the way in which a thermonuclear spacecraft engine might work. Furthermore, as there are now indications that quantum physics might allow a spacecraft to draw energy from the vacuum as it travels, the thermonuclear engines might not be the only source of fuel. Additionally, Frederick said that the Gainer assumed that nuclear fusion is the best form of energy. He disagreed saying that particle / anti-particle annihilation was a better alternative. Finally, he said, there’s no reason one couldn’t go slower and use less fuel, if you, for instance, freeze the crew.

If Dr. Fredrick knows how to obtain antimatter to use as fuel, and how to control and constrain it, we would be very interested to know this. "Zero point" quantum energy from space is a common woo-physics claim (see, for example, Dr. Harold Puthoff), but is not accepted by mainstream physics.

Huston adds a few more lame suggestions, such as "Couldn’t it use solar sails catching photons and the gravitational forces of planets and other astronomical objects to help slow itself?" He obviously doesn't have a clue concerning the magnitude mass and the momentum of the craft. One could much more easily use solar sails to stop a speeding freight train than a massive spaceship traveling at half the speed of light. Huston concludes, "We [skeptics] are supposed to be the people who read, question and think—not the ones who blindly repeat assertions that fit our pre-conceived notions. I think we, as skeptics, need to be more careful of such statements and false conclusions. They only hurt us in the end." As if the need to obey the laws of physics were a 'pre-conceived notion.'

Gainer's response to Huston is in the following issue of E-Skeptic, and begins by noting the difference between "belief systems and science... A belief system need not concern itself with objective reality. This contrasts with science in which theories are subject to objective evaluation by repeated experiment and measurement. Science assumes a priori the existence of a measurable objective reality. Indeed, science is the delineation of this reality." He continues, "any spacecraft, whether from present or future technology, would have a significant inertial mass. Ten thousand years from now conservation of energy will apply anywhere in the galaxy as well as it does today."

As for the objection that magical future technologies could somehow build substances that can be used to constrain fusion reactions, "because of the maximum cohesive force that electrons can create between protons no substance will remain solid above 5000ºC. " The temperature of a nuclear fusion reaction is on the order of 10,000,000 degrees C. That has nothing to do with present-day, or future technologies. It is because the energy of the strong nuclear force released in the fusion reaction is overwhelmingly more powerful than the weak electromagnetic bonds that hold atoms and molecules together. But the Star Trek Skeptics don't want to hear this. They want to believe that some future technological wizard will invent a super-glue whose atomic binding is even stronger than the strong nuclear force. Gainer concludes, "It is not present or future technology that negates interstellar travel—it is the nature and structure of matter and the universe."

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About Me

Robert Sheaffer is a writer with a lifelong interest in astronomy and the question of life on other worlds. He is one of the leading skeptical investigators of UFOs, a founding member of the UFO Subcommittee of the well-known Committee for Skeptical Inquiry (CSI, formerly CSICOP). He is also a founding director and past Chairman of the Bay Area Skeptics, a local skeptics' group in the San Francisco Bay area .
Mr. Sheaffer has written the "Psychic Vibrations" column in The Skeptical Inquirer for over 30 years, and his book "Psychic Vibrations" reprints some of those columns. He is also the author of "UFO Sightings" (Prometheus Books, 1998), and has appeared on many radio and TV programs. His writings and reviews have appeared in such diverse publications as OMNI, Scientific American, Spaceflight, Astronomy, The Humanist, Free Inquiry, Reason, and others.
Mr. Sheaffer lives near San Diego, California. He has worked as a data communications engineer in the Silicon Valley, and sings in professional opera productions.